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PERF: optimize Block.getitem_block #34978

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Merged
merged 1 commit into from
Jun 25, 2020
Merged

PERF: optimize Block.getitem_block #34978

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1 change: 1 addition & 0 deletions pandas/_libs/internals.pyx
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@ cnp.import_array()
from pandas._libs.algos import ensure_int64


@cython.final
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do these actually make a diff?

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i havent measured this independently, so not sure how much it matters in this case (tried it for some Timestamp methods and got a decent boost). it allows cython to do some inlining, at the cost of disallowing subclassing.

cdef class BlockPlacement:
# __slots__ = '_as_slice', '_as_array', '_len'
cdef:
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18 changes: 17 additions & 1 deletion pandas/core/internals/blocks.py
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Expand Up @@ -8,6 +8,7 @@

from pandas._libs import NaT, algos as libalgos, lib, writers
import pandas._libs.internals as libinternals
from pandas._libs.internals import BlockPlacement
from pandas._libs.tslibs import conversion
from pandas._libs.tslibs.timezones import tz_compare
from pandas._typing import ArrayLike
Expand Down Expand Up @@ -112,6 +113,19 @@ class Block(PandasObject):
_verify_integrity = True
_validate_ndim = True

@classmethod
def _simple_new(
cls, values: ArrayLike, placement: BlockPlacement, ndim: int
) -> "Block":
"""
Fastpath constructor, does *no* validation
"""
obj = object.__new__(cls)
obj.ndim = ndim
obj.values = values
obj._mgr_locs = placement
return obj

def __init__(self, values, placement, ndim=None):
self.ndim = self._check_ndim(values, ndim)
self.mgr_locs = placement
Expand Down Expand Up @@ -289,13 +303,15 @@ def getitem_block(self, slicer, new_mgr_locs=None):
if new_mgr_locs is None:
axis0_slicer = slicer[0] if isinstance(slicer, tuple) else slicer
new_mgr_locs = self.mgr_locs[axis0_slicer]
elif not isinstance(new_mgr_locs, BlockPlacement):
new_mgr_locs = BlockPlacement(new_mgr_locs)

new_values = self._slice(slicer)

if self._validate_ndim and new_values.ndim != self.ndim:
raise ValueError("Only same dim slicing is allowed")

return self.make_block_same_class(new_values, new_mgr_locs)
return type(self)._simple_new(new_values, new_mgr_locs, self.ndim)

@property
def shape(self):
Expand Down